<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <script type="text/javascript" src="../assets/js/vue.js"></script>
    <title>Example Event Demo</title>
</head>
<body>
    <h1>Example Event Demo</h1>
    <hr>
    <div id="app">
        <p>{{num}}</p>
        <button @click="add">add</button>
        
    </div>
     <p><button onclick="reduce()">reduce</button></p>
     <p><button onclick="reduceOnce()">reduceOnce</button></p>
     <p><button onclick="off()">off</button></p>
     

    <script type="text/javascript">
        var app=new Vue({
            el:'#app',
            data:{num:1},
            methods:{
                add:function(){
                    this.num++;
                }
            }
        })
        //实例事件
        app.$on('reduce',function(){
            console.log('执行了reduce()');
            this.num--;
        });
        //只使用一次的实例方法
        app.$once('reduceOnce',function(){
            console.log('只执行一次的方法');
            this.num--;

        });

        //关闭事件
        function off(){
            app.$off('reduce');
        }

//外部调用内部事件
function reduce(){
    app.$emit('reduce');
}
        function reduceOnce(){
            app.$emit('reduceOnce');
        }

     
    </script>
</body>
</html>